MDB2 Error on Update

[Ninerian]

Hello,

I just trying to update my version of roundcube from 0.1RC1 to
the latest.
I just copied all files and changed the main.inc.php.

When I open /roundcube/install/ following text appears:

RoundCube Webmail Installer

   1. Check environment
   2. Create config
   3. Test config

Check config files
main.inc.php:  OK
db.inc.php:  OK
Replaced config options

The following config options have been replaced or renamed. Please update them accordingly in your config files.

    * skin_path was replaced by skin
    * locale_string was replaced by language

Obsolete config options

You still have some obsolete or inexistent properties set. This isn't a problem but should be noticed.

    * db_backend

OK, lazy people can download the updated config files here: main.inc.php  db.inc.php
Check if directories are writable

RoundCube may need to write/save files into these directories
temp/:  OK
logs/:  OK
Check configured database settings
DSN (write):  OK
DB Schema:  OK

Catchable fatal error: Object of class MDB2_Error could not be converted to string in /www/htdocs/w007d6d2/webmail/program/lib/MDB2/Driver/mysql.php on line 1109

I dont know, how to get rid of this error. Some research no the web returns a problem between MDB2 and PHP 5.2.5, which my server runs.

Could you please help me?

Thank you